I havent caught up yet on all the posts since yesterdays great webcast (Thanks, Tricia!), but just to make sure were all on the same page on the blanching/lividity issue before moving on...
DD, I hope you know how much I value your knowledge. I dont have the medical background you do, so I can only follow along on the discussions about the reasons that certain things happen (metabolic, chemical, etc. changes). I do know though that if you press on the skin of a living person, when you remove the pressure it will be white for a few seconds because the blood has been suppressed. With the pressure removed and as the blood returns, it will come back to its natural color. Not that I have ever tried this, but if I did the same thing to the skin of a dead person (depending of course on how long after death), when I remove the pressure, the blood will not return (because of all the reasons you stated above).
The reason for clearing that up is because we can disagree on the interpretation of what that means, but we need to agree first on the facts.
Based on all this, if I understand your theory correctly, you believe the blanched area to have been formed by something other than the cord after the upper ligature was in place and after death had occurred. I cant disagree with that as a possibility based on our understanding of the physiological aspects.
However, I do believe in a little different sequence of events, which I dont believe you can dispute by the same understanding of those physiological aspects. I believe the blanched area occurred first and caused her death (along with the head blow). Because of the angle of the lower circumference, it tells us the direction of force pulling on the cord (I believe the same cord that was left on her neck). Because of the direction of the force pulling on the cord there, it is unlikely that it was done facing her. IOW, the person or force pulling on the cord had to have been behind her when it happened. The reason for no defensive scratch marks on her neck is because she was unconscious from the head blow. Shortly after she expired, the cord was moved to the upper position where it remained until her body was found about 12 hours later. (Again, note the angle of the furrow in the relation to the blanched circumference.)
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I actually DO believe the ligature made BOTH the red and white marks on her neck. IMO I do not believe there are marks from anything else on her neck.